/*
 * Copyright 1999-2004 The Apache Software Foundation.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */ 

package org.apache.taglibs.standard.lang.jstl;

/**
 *
 * <p>This class is used to customize the way the evaluator resolves
 * variable references.  For example, instances of this class can
 * implement their own variable lookup mechanisms, or introduce the
 * notion of "implicit variables" which override any other variables.
 * An instance of this class should be passed to the evaluator's
 * constructor.
 *
 * <p>Whenever the evaluator is invoked, it is passed a "context"
 * Object from the application.  For example, in a JSP environment,
 * the "context" is a PageContext.  That context object is eventually
 * passed to this class, so that this class has a context in which to
 * resolve variables.
 * 
 * @author Nathan Abramson - Art Technology Group
 * @version $Change: 181177 $$DateTime: 2001/06/26 08:45:09 $$Author: pierred $
 **/

public interface VariableResolver
{
  //-------------------------------------
  /**
   *
   * Resolves the specified variable within the given context.
   * Returns null if the variable is not found.
   **/
  public Object resolveVariable (String pName,
				 Object pContext)
    throws ELException;
					
  //-------------------------------------
}
